When I upgraded SDM 12.9 to 126.96.36.199 I noticed that File Types from Attachment Library Menu is missing.
Due to changes in the application this separate option no longer is needed.
Release : 17.2
Component : SERVICE DESK MANAGER
Restrictions for certain extensions can be added to the Repository itself. This can be done by going to the Administration tab, then "Attachments Library". In there go to "Repositories" and right click on the desired Repository and view the details.
From here you can define restrictions for extensions